• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.262-268
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• 2003

This paper describes the effect of loading rate, specimen geometries and material properties for Mode I interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) specimen. In the range of loading rate 0.2-20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (G_IC). The value of $G_IC$ for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of $G_IC/$ are highest with the increasing initial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.89-92
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• 2008

This study investigates the shear behavior of architectural masonry veneer wall reinforced with specific reinforcement details proposed by this study. For this purpose, experimental tests were conducted using one un-reinforced masonry(URM) wall specimen and three reinforced masonry(RM) wall specimens under quasi static cyclic loads. Un-reinforced(plain) masonry wall is expressed that behavior and failure mode are different for aspect ratio(L/H) and axial compressive force. The test variables are wall aspect ratio and presence of reinforcement. These specimens are masonry structure for architectural clading that is not to exist the axial compressive force. thus the axial compressive force is excepted from test variable. Test result, Behavior of specimens are dominated over rocking mode, but final failure modes are combined with different behaviors. And FEMA273 has proposed the equation of shear strength of masonry pier subjected to in-plane loading. Shear strength equations are classified four types of failure mode that is Rocking, and Toe-Crushing, Bed-Joint-Sliding and Diagonal-Tension. FEMA273 equations predict the behavior modes well, but shear strength is shown in different result.

• Composites Research
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• v.22 no.6
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• pp.23-31
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• 2009

This paper investigated acoustic emission (AE) characteristics in association with various fracture processes of glass fiber reinforced plastic skin/ aluminum honeycomb core (GF-AH) hybrid composites under compressive and bending loads. Various failure modes such as skin layer fracture, skin/core interfacial fracture, and local plastic yield buckling and cell wall adhesive fracture occurring in the honeycomb cell wall were classified through the fracture identification in association with the AE frequency and amplitude analysis. The distribution of the event-rate in which it has a high amplitude showed a procedure of cell wall adhesive fracture, skin/core interfacial debonding and fiber breakage, whereas distribution of different peak frequencies indicated the plastic deformation of aluminum cell wall and the friction between honeycomb walls. Consequently, the fracture behaviors of GF-AH hybrid composites could be characterized through a nondestructive evaluation employing the AE technique.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.17-25
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• 2010

Evaluation of stability in traditional designing of reinforced soil structures is executed by examination of internal and external stability. Analysis of internal stability is for pull-out and ductile strength. Analysis of external stability is for settlement, overturning and sliding. To minimize inherent uncertainties of soil properties and analytical model, reliability analysis was developed recently. In this study, reliability analysis method considering simultaneous failure probability for various failure mode of internal and external stability is proposed. By applying uni-modal bounds, Stability of system reliability of reinforced soil structures is evaluated by integrating multi failure mode for various analytical model. Because of complex consideration for various failure shapes and modes, it is possible to secure advanced safety by using simultaneous failure probability. And evaluation of reinforced soil structure is executed by representative index, simultaneous failure probability, than previous method.

• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.395-402
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• 2007

Probabilistic risk assessment was conducted on a hybrid cable-stayed bridge consisting of a steel-composite plate girder and a concrete girder with a long span, designed using the working stress design and strength design methods. The component reliabilities of the bridge's cables, pylons, girders, and steel-concrete conjunction were evaluated using the AFOSM(Advanced First Order Second Moment) algorithm and the simulation technique at the critical sections, based on the maximum axial force, shear, and positive and negative moments of the selected sections. For the analysis of system reliability, the hybrid cable-stayed bridge consisting of cables, pylons, and plate girders was modeled into combined failure modes, and for system reliability, the probabilities of failure and reliability index of the structural system were evaluated. Based on the results of this study, the critical failure modes of the hybrid cable-stayed bridge based on the bridge's structural characteristics are suggested, and the efficiency of the partial ETA technique for use in the risk assessment method was confirmed.

• Composites Research
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• v.35 no.2
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• pp.61-68
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• 2022

Composite materials have been used in aerospace industry and many applications because of many advantages such as specific strength and stiffness and corrosion resistance etc. However, it is vulnerable to impacts, these impact lead to formation of cracks in composite laminate and failure of structures. In this paper, we analyzed Mode I fracture toughness of Carbon/Epoxy laminates using acoustic emission signal. DCB test was carried out to analyze Mode I failure characterization of Carbon/Epoxy laminates, and AE sensor was attached to measure AE signal induced by failure of specimen. Fracture toughness was calculated using cumulative AE energy and measured crack length using camera. The calculated fracture toughness was applied in FE model and the result of FE analysis compared with DCB test results. The results show good agreement with between FEM and DCB test results.

• Composites Research
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• v.30 no.1
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• pp.52-58
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• 2017

This paper presents the optimum design methodology for composite wing structure which automatically calculates the safety margin using optimization framework integrating failure modes. Particularly, its framework is possible to optimize sizing procedure to prevent failure mode which has the greatest effect on reducing the sizing time of composite structure. The main failure mode was set as the first ply failure, buckling failure mode, and bolted joint stress field, and the margin was calculated to minimize the weight. The design variable is a laminate sequence database and the responses are strain, buckling, bolted joint stress field. The objective function is the mass of the wing structure. The results of buckling analysis were compared using the finite element model to verify the robustness and reliability of Composite Optimizer.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.862-868
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• 2013

The mechanics of woven fabric-based laminated composites is complex. Then, many researchers have studied woven fabric CFRP materials but fracture resistance behaviors for composites have not been still standardized. It also shows the different behavior according to load and fiber direction. Therefore, there is a need to consider fracture resistance behavior in conformity with load and fiber direction at designing structure using woven CFRP materials. In this study, therefore, the tensile strength and resistance for plain-weave CFRP composite materials were investigated under various different angle condition(load to fiber angle: $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$). Tensile strength and fracture toughness tests were carried out under mode I transverse crack opening load by using compact tension specimens.

• Composites Research
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• v.19 no.4
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• pp.15-22
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• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

• Composites Research
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• v.22 no.6
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• pp.32-38
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• 2009

In this study, the energy absorption capabilities and failure modes of four different kinds of circular tubes made of carbon, Kevlar and carbon-Kevlar hybrid composites with epoxy resin have been evaluated. In order to achieve these goals, these tubes were fabricated with unidirectional prepregs and compressive tests were conducted for the tubes under 10mm/min loading speed. From the test results, carbon/epoxy tubes were collapsed by brittle fracturing mode and showed the best energy absorption capabilities, while Kevlar/epoxy tubes were crushed by local buckling mode and worst. The hybrid [$90_C/0_K$] tubes were failed in a local bucking mode and showed good post crushing integrity, whereas [$90_K/0_C$] tubes were failed in a lamina bending mode and bad post crushing integrity.